Speaking in New York City yesterday, Sanders reiterated his support for Warren's legislation to reinstate the Glass-Steagall Act, a 1933 statute that separated plain-vanilla commercial banks from riskier investment banks but was repealed under a bipartisan 1999 law signed by President Bill Clinton. Critics of Clinton's deregulation assert that the repeal of the law helped pave the way for the 2008 financial crisis, encouraging the creation of too-big-to-fail megabanks.

In a series of tweets Wednesday morning, Warren decried the continued existence of such institutions and applauded Sanders for his efforts to "hold big banks accountable":

11 big banks are still so risky that if any one started to fail, they'd need a gov bailout or risk taking down the economy - again.

But the 2016 Republicans claim they'll repeal all the new financial regulations - hoping to be chosen as Wall Street's favorite candidate.

I'm glad @BernieSanders is out there fighting to hold big banks accountable, make our economy safer, & stop the GOP from rigging the system.

We need to level the playing field and end too big to fail.

A coveted endorsement: Warren, who remains neutral in the Democratic presidential race, has also lauded frontrunner Hillary Clinton for her own proposals to rein in Wall Street, despite past criticism that Clinton was too close to the financial industry.

Last month, after Clinton published a New York Times op-ed calling for fees on systemically risky institutions and vowing to push back against GOP efforts to pare back the 2010 Dodd-Frank financial reform law, Warren tweeted a link to her followers, writing, "I agree with @HillaryClinton."

With the Democratic Party adopting an increasingly progressive line on financial issues following the Great Recession, Warren's praise lends the candidates heft in the liberal populist community that once sought to draft Warren into the 2016 race. While Warren didn't heed those calls, she recently told the Boston Globethat she would likely endorse a candidate in the Democratic primary, but that she didn't have a timetable for making that decision.

For Sanders, who's seeking to arrest Clinton's momentum as the Iowa caucuses approach, a Warren endorsement would bring a major shot of adrenaline. Warren suggested last summer that she was open to endorsing Sanders, but she also signed a 2013 letter from Democratic women senators urging Clinton to mount a bid.